Expandable sheath with longitudinally extending reinforcing members

ABSTRACT

An expandable delivery sheath includes an elastic outer tubular layer and an inner tubular layer. The inner tubular layer include a thick wall portion integrally connected to a thin wall portion. The thin wall portion can include longitudinal reinforcing members/rods that facilitate unfolding during the passage of the implant, thus decreasing the push force and increasing the consistency of the push force. The inner tubular layer can have a non-expanded or folded condition wherein the thin wall portion folds onto an outer surface of the thick wall portion under urging of the elastic outer tubular layer. When an implant passes therethrough, the outer tubular layer stretches and the inner tubular layer unfolds into an expanded lumen diameter. Once the implant passes, the outer tubular layer again urges the inner tubular layer into the non-expanded condition with the sheath reassuming its smaller profile.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Application No. 17/068,632,filed Oct. 12, 2020, which is a continuation of U.S. Application No.15/914,748, filed on Mar. 7, 2018, (now Pat. No. 10,799,685), whichclaims the benefit of priority to U.S. Provisional Application No.62/469,121, filed Mar. 9, 2017. Each of the aforementioned applicationsis incorporated by reference in its entirety for all purposes.

FIELD

The present application is directed to a sheath for use withcatheter-based technologies for repairing and/or replacing heart valves,as well as for delivering an implant, such as a prosthetic valve to aheart via the patient’s vasculature.

BACKGROUND

Endovascular delivery catheter assemblies are used to implant prostheticdevices, such as a prosthetic valve, at locations inside the body thatare not readily accessible by surgery or where access without invasivesurgery is desirable. For example, aortic, mitral, tricuspid, and/orpulmonary prosthetic valves can be delivered to a treatment site usingminimally invasive surgical techniques.

An introducer sheath can be used to safely introduce a deliveryapparatus into a patient’s vasculature (e.g., the femoral artery). Anintroducer sheath generally has an elongated sleeve that is insertedinto the vasculature and a housing that contains one or more sealingvalves that allow a delivery apparatus to be placed in fluidcommunication with the vasculature wit0h minimal blood loss. Aconventional introducer sheath typically requires a tubular loader to beinserted through the seals in the housing to provide an unobstructedpath through the housing for a valve mounted on a balloon catheter. Aconventional loader extends from the proximal end of the introducersheath, and therefore decreases the available working length of thedelivery apparatus that can be inserted through the sheath and into thebody.

Conventional methods of accessing a vessel, such as a femoral artery,prior to introducing the delivery system include dilating the vesselusing multiple dilators or sheaths that progressively increase indiameter. This repeated insertion and vessel dilation can increase theamount of time the procedure takes, as well as the risk of damage to thevessel.

Radially expanding intravascular sheaths have been disclosed. Suchsheaths tend to have complex mechanisms, such as ratcheting mechanismsthat maintain the shaft or sheath in an expanded configuration once adevice with a larger diameter than the sheath’s original diameter isintroduced.

However, delivery and/or removal of prosthetic devices and othermaterial to or from a patient still poses a risk to the patient.Furthermore, accessing the vessel remains a challenge due to therelatively large profile of the delivery system that can causelongitudinal and radial tearing of the vessel during insertion. Thedelivery system can additionally dislodge calcified plaque within thevessels, posing an additional risk of clots caused by the dislodgedplaque.

U.S. Pat. No. 8,790,387, which is entitled “Expandable Sheath forIntroducing an Endovascular Delivery Device into a Body” and isincorporated herein by reference, discloses a sheath with a split outerpolymeric tubular layer and an inner polymeric layer. A portion of theinner polymeric layer extends through a gap created by the cut and canbe compressed between the portions of the outer polymeric tubular layer.Upon expansion of the sheath, portions of the outer polymeric tubularlayer have separated from one another, and the inner polymeric layer isexpanded to a substantially cylindrical tube. Advantageously, the sheathdisclosed in the ‘387 patent can temporarily expand for passage ofimplantable devices and then return to its starting diameter.

U.S. Pat. Application No. 14/880,109, titled “Expandable Sheath” anddescribed in U.S. Pat. Application Publication No. 2016/0296730,incorporated herein by reference, discloses an inner tubular memberhaving a longitudinally extending thin wall portion that is foldedbetween surrounding thick wall portions when the inner tubular member isin the non-expanded state. This thin segment facilitates the expansionand collapse of the inner tubular layer while also maintaining a fluidseal to prevent leakage during use.

Despite the disclosures of the ‘387 patent and the ‘109 application,there remains a need for further improvements in introducer sheaths forendovascular systems used for implanting valves and other prostheticdevices. Even further reduction of the profile is desirable to providethe most protection for the vascular wall. However, reduction of theprofile tends to increase the necessary push force (the force requiredto push a device through the sheath). It is helpful if the consistencyof the push force is maintained as the device travels the length of thesheath, but this can be difficult to achieve. For example, the processof unfolding the inner tubular layer of the sheath described inapplication ‘109 can create inconsistency in the necessary push force.These inconsistencies can result in a practitioner using more force thanis needed to pass a difficult spot, possibly causing unnecessary damageto the vascular wall.

SUMMARY

Disclosed herein are low-profile expandable introducer sheaths andmethods of using the same to achieve low and consistent push forceduring intravascular procedures. The sheaths are adapted to temporarilyexpand a portion of the sheath to allow for the passage of a deliverysystem for a cardiovascular device, then return to a non-expanded stateafter the passage of the system. The sheath includes an elastic outertubular layer and an inner tubular layer through which thecardiovascular device and its delivery system pass. The inner tubularlayer includes a thick wall portion integrally connected to a thin wallportion. The thick wall portion having a first and second longitudinallyextending end, the thin wall portion extending therebetween. The thinwall portion includes at least one longitudinal rod/reinforcing memberextending along a length of the thin wall portion. When the implantpasses therethrough, the outer tubular layer stretches and the innertubular layer at least partially unfolds to a larger expanded diameterto accommodate the diameter of the implant. Once the implant passes, theouter tubular layer again urges the inner tubular layer into the foldedconfiguration with the sheath reassuming its smaller profile. The sheathcan also include selectively placed longitudinal rods that mediatefriction between the inner and outer tubular layers, or between folds ofthe inner tubular layer to facilitate easy expansion and collapse. Thisreduces the overall push force and increases the consistency of the pushforce needed the advance the oversized implant through the sheath’slumen. The lower and more consistent push force facilitates a reductionin the profile size. Furthermore, the integral construction of the innertubular layer guards against the leaks and snags of prior art split-tubeand uniform thickness liner combinations.

Embodiments include an expandable sheath including an elastic outertubular layer and an inner tubular layer. The inner tubular layer has athick wall portion integrally connected to a thin wall portion - such asby co-extrusion during manufacture. The thick wall portion having afirst and second longitudinally extending end, the thin wall portionextending therebetween. The thin wall portion can include a longitudinalrod/reinforcing member extending along a length of the thin wallportion. The elastic outer tubular layer and the inner tubular layer canbe radially movable between an expanded state and a non-expanded state.In the non-expanded state the elastic outer tubular layer can urge thefirst longitudinally extending end towards and/or under the secondlongitudinally extending end of the inner tubular layer. In the expandedstate, the first and second longitudinally extending ends of the innertubular layer expand apart with the thin wall portion extendingtherebetween. The outer elastic tubular layer can urge the inner tubularlayer towards the non-expanded state. The outer diameter of the elasticouter tubular layer can be from 10 French to 14 French in thenon-expanded state. In an example sheath, the distal portion of theouter tubular layer and a distal portion of the inner tubular layer areadhered to each other in a sealed configuration.

The longitudinal rods can extend within in the thin wall portion of theinner tubular layer such that the rod has a thickness no greater than athickness of the thin wall portion. A surface of the rod can protrudefrom a surface of the inner tubular layer. In an example sheath, thesurface of the rod can protrude from an inner surface of the innertubular layer such that the surface of the rod facilitates relativemovement between the inner tubular layer and a passing device. Inanother example sheath, the surface of the rod can protrude from anouter surface of the inner tubular layer such that the surface of therod facilitates relative movement between the inner tubular layer andthe outer tubular layer. In another example sheath, a first portion ofan outer surface of the rod can protrude from an inner surface of theinner tubular member and a second portion of the outer surface of therod can protrude from an outer surface of the inner tubular layer. Thelongitudinal rod can extend along the entire length of the inner tubularlayer. The longitudinal rod can have a curvilinear, rectilinear, andirregular shape in cross-section. In one example embodiment, the rod hasa circular shape in cross-section.

In another embodiment, the longitudinal rods can also be included on thethick wall portion of the inner tubular layer. In an example sheath, theouter tubular layer can include a plurality of longitudinal rods, aportion of each of the plurality of longitudinal rods extending into acentral lumen defined by the outer tubular layer such that the pluralityof longitudinal rods provide a bearing surface to facilitate relativemovement of the inner tubular layer within the outer tubular layer whenmoving between the expanded and non-expanded state. In another examplesheath, a distal portion of the outer tubular layer and a distal portionof the inner tubular layer are adhered to each other in a sealedconfiguration.

A method of delivering a device into the blood vessel of a patient usingthe expandable introducer sheath can include inserting an expandablesheath at an implantation site within the blood vessel of the patientand advancing the device through a lumen of the expandable sheath. Thesheath can include a thick wall portion and a thin wall portionextending between longitudinally extending ends of the thick wallportion, the thin wall portion including a longitudinally extendingreinforcing member extending along a length of the thin wall portion.The method can further include locally expanding a portion of the sheathfrom a non-expanded state to an expanded state by a radially outwardforce provided at an inner surface of the sheath by advancement of thedevice, such that expansion of the sheath causes the longitudinallyextending ends of the inner tubular layer to expand apart with the thinwall portion extending therebetween. Upon passage of the device from theportion of the sheath, the portion of the sheath can be locallycontracted from the expanded state at least partially back to anon-expanded state. In the non-expanded state, the longitudinallyextending ends of the thick wall portion can overlap such that the thinwall portion extends between the overlapping portions of the thick wallportion. In the expanded state, the longitudinally extending ends canexpand apart with the thin wall portion extending therebetween.

In an example sheath, the longitudinally extending ends of the thickwall portion can include a first longitudinally extending end and asecond longitudinally extending end. Locally expanding a portion of thesheath can further include incrementally expanding the sheath, the firstincrement of expansion provided between the first longitudinallyextending end and the reinforcing member, the second increment ofexpansion provided between the reinforcing member and the secondlongitudinally extending end.

In another example sheath, the longitudinally extending ends of thethick wall portion can include a first longitudinally extending end anda second longitudinally extending end. The thin wall portion of theexpandable sheath can further include a first and a secondlongitudinally extending reinforcing member. Locally expanding a portionof the sheath can further comprise incrementally expanding the sheath,the first increment of expansion provided between the firstlongitudinally extending end and the first reinforcing member, thesecond increment of expansion provided between first reinforcing memberand the second reinforcing member, the third increment of expansionprovided between the second reinforcing member and the secondlongitudinally extending end.

Locally contracting the sheath can comprise providing inwardly directedradial force of an elastic outer layer that exerts a radiallycompressive force urging the sheath towards the non-expanded state.

In an example sheath, the longitudinally extending ends of the thickwall portion include a first longitudinally extending end and a secondlongitudinally extending end. Locally contracting the sheath furthercomprises moving the first and second longitudinally extending endstowards each other and into an overlapping configuration.

DESCRIPTION OF DRAWINGS

FIGS. 1A-1C show a delivery catheter assembly for delivering aprosthetic implant.

FIG. 2 is a cross-section of both the inner and outer tubular layers ofthe sheath in a non-expanded state.

FIG. 3 is a perspective view of the distal end of an example expandablesheath.

FIG. 4 is a cross-section of an example inner tubular layer of thesheath.

FIG. 5 is a cross-section of an example outer tubular layer of thesheath.

FIGS. 6A-6C are cross-sections of an example sheath includinglongitudinal rods in the inner tubular layer.

FIGS. 7A-7C are cross-sections of an example sheath includinglongitudinal rods in the inner tubular layer.

FIGS. 8A-8C are cross-sections of an example sheath includinglongitudinal rods in the inner tubular layer.

FIG. 9 is a cross-section of an example outer tubular layer of thesheath.

FIG. 10 is a magnified view of part of the outer tubular layer of FIG. 9, showing the cross section of longitudinal rods in greater detail.

FIG. 11 is a cross-section of an example sheath including longitudinalrods embedded in the outer tubular layer.

FIG. 12 is a cross-section of an example sheath including longitudinalrods embedded in the outer tubular layer.

FIG. 13 is a cross-section of an example sheath including longitudinalrods embedded in the outer tubular layer.

FIG. 14 is a cross-section of an example sheath including longitudinalrods embedded in the outer tubular layer.

FIG. 15 is a cross-section of an example sheath including longitudinalrods embedded in the outer tubular layer and the inner tubular layer.

DETAILED DESCRIPTION

The following description of certain examples of the inventive conceptsshould not be used to limit the scope of the claims. Other examples,features, aspects, embodiments, and advantages will become apparent tothose skilled in the art from the following description. As will berealized, the device and/or methods are capable of other different andobvious aspects, all without departing from the spirit of the inventiveconcepts. Accordingly, the drawings and descriptions should be regardedas illustrative in nature and not restrictive.

For purposes of this description, certain aspects, advantages, and novelfeatures of the embodiments of this disclosure are described herein. Thedescribed methods, systems, and apparatus should not be construed aslimiting in any way. Instead, the present disclosure is directed towardall novel and nonobvious features and aspects of the various disclosedembodiments, alone and in various combinations and sub-combinations withone another. The disclosed methods, systems, and apparatus are notlimited to any specific aspect, feature, or combination thereof, nor dothe disclosed methods, systems, and apparatus require that any one ormore specific advantages be present or problems be solved.

Features, integers, characteristics, compounds, chemical moieties, orgroups described in conjunction with a particular aspect, embodiment orexample of the invention are to be understood to be applicable to anyother aspect, embodiment or example described herein unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract, and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The invention is notrestricted to the details of any foregoing embodiments. The inventionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract, and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

It should be appreciated that any patent, publication, or otherdisclosure material, in whole or in part, that is said to beincorporated by reference herein is incorporated herein only to theextent that the incorporated material does not conflict with existingdefinitions, statements, or other disclosure material set forth in thisdisclosure. As such, and to the extent necessary, the disclosure asexplicitly set forth herein supersedes any conflicting materialincorporated herein by reference. Any material, or portion thereof, thatis said to be incorporated by reference herein, but which conflicts withexisting definitions, statements, or other disclosure material set forthherein will only be incorporated to the extent that no conflict arisesbetween that incorporated material and the existing disclosure material.

As used in the specification and the appended claims, the singular forms“a,” “an” and “the” include plural referents unless the context clearlydictates otherwise. Ranges may be expressed herein as from “about” oneparticular value, and/or to “about” another particular value. When sucha range is expressed, another aspect includes from the one particularvalue and/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another aspect. It will befurther understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where said event or circumstance occurs and instances where itdoes not.

Throughout the description and claims of this specification, the word“comprise” and variations of the word, such as “comprising” and“comprises,” means “including but not limited to,” and is not intendedto exclude, for example, other additives, components, integers or steps.“Exemplary” means “an example of” and is not intended to convey anindication of a preferred or ideal aspect. “Such as” is not used in arestrictive sense, but for explanatory purposes.

The terms “proximal” and “distal” as used herein refer to regions of asheath, catheter, or delivery assembly. “Proximal” means that regionclosest to handle of the device, while “distal” means that regionfarthest away from the handle of the device.

Disclosed herein are elongate, expandable introducer sheaths that areparticularly suitable for use in the delivery of implants in the form ofimplantable heart valves, such as balloon-expandable implantable heartvalves. Balloon-expandable implantable heart valves are well-known andwill not be described in detail here. An example of such an implantableheart valve is described in U.S. Pat. No. 5,411,552, and also in U.S.Pat. Application Publication No. 2012/0123529, both of which are herebyincorporated by reference. The elongate expandable introducer sheathsdisclosed herein can also be used with the delivery systems for othertypes of implantable devices, such as self-expanding implantable heartvalves, stents or filters. The term “implantable” as used herein isbroadly defined to mean anything - prosthetic or not - that is deliveredto a site within a body. A diagnostic device, for example, can be animplantable.

Disclosed embodiments of an expandable introducer sheath can minimizetrauma to the vessel by allowing for temporary expansion of a portion ofthe introducer sheath to accommodate the implantable device and itsdelivery system, then return fully or partially to the original,non-expanded diameter after passage of the device. The expandable sheathcan include an integrally formed inner tubular layer with thick and thinwall portions. The thin wall portion can expand to provide an expandedcentral lumen to allow passage of an implant. The inner layer folds backonto itself under biasing of an outer elastic tubular layer followingpassage of the implant.

In another aspect, the expandable sheath can include one or morelongitudinally oriented stiffening elements, such as rods. When coupledto the thin wall portion of the inner tubular layer, the longitudinalrods facilitate unfolding during expansion, decreasing the required pushforce to move the device through the sheath while also increasing theconsistency of the push force. The push force is decreased because thelongitudinal rods lower the friction between the surfaces of the thinand thick wall segments when the inner tubular member is in a foldedstate, making it easier for them to slide against each other duringunfolding. The longitudinal rods also improve the consistency of thepush force by causing unfolding to occur at specific points along thethin wall segment.

Some embodiments can comprise an expandable introducer sheath with asmaller profile than the profiles of prior art introducer sheaths. Thesmaller profiles are made possible, at least in part, by the lower andmore consistent push force. Finally, present embodiments can reduce thelength of time a procedure takes, as well as reduce the risk of alongitudinal or radial vessel tear, or plaque dislodgement, because onlyone introducer sheath is required, rather than several different sheathsof gradually increasing diameters. Embodiments of the present expandablesheath can avoid the need for multiple insertions for the dilation ofthe vessel.

FIGS. 1A-1C illustrate a sheath 10 according to the present disclosurein use with a representative delivery apparatus 110 for delivering aprosthetic implant 112, such as a prosthetic heart valve, to a patient.It should be understood that the delivery apparatus 110 described hereinis exemplary only, and that other similar delivery systems can of coursebe used with the expandable sheath 10. The delivery apparatus 110generally includes a steerable guide catheter 114 and a balloon catheter116 extending through the guide catheter 114.

The guide catheter 114 and the balloon catheter 116 illustrated in FIGS.1A-1C are adapted to slide longitudinally relative to each other tofacilitate delivery and positioning of prosthetic heart valve 112 at animplantation site in a patient’s body, as described in detail below. Theguide catheter 114 includes a handle portion 120 coupled to an elongatedguide tube/shaft 122 (FIG. 1B).

FIG. 1C provides a perspective view of an expandable sheath 10 that isused to introduce the delivery apparatus 110 into the patient’s body.The expandable sheath 10 has a central lumen to guide passage of thedelivery system for the prosthetic heart valve 112. At a proximal endthe expandable sheath 10 includes a hemostasis valve that preventsleakage of pressurized blood. Generally, during use a distal end of thesheath 10 is passed through the skin of the patient and inserted into avessel, such as the femoral artery. The delivery apparatus 110 is theninserted into the sheath 10 through the hemostasis valve, and advancedthrough the patient’s vasculature where the implant 112 is delivered andimplanted within the patient.

As outlined above, the sheath 10 includes an inner tubular layer 42 andouter tubular layer 40. In FIG. 1C only the outer tubular layer 40 isvisible. The sheath 10 comprises a proximal end 3 and distal end 5opposite the proximal end 3. The sheath 10 can include a taper tube 70,a flared proximal end. The taper tube 70 can be coextruded with thesheath 10 or added to the proximal end 3 by flaring and bonding theinner and outer tubular layers 42, 40. The distal end 5 of the sheath 10can define a tubular structure with a slightly tapering orfrusto-conical distal end. The structure of the distal tip of the sheath10 helps to increase the structural rigidity of the distal end of thetubular wall structure, blocks blood flow between the layers andprovides a smooth, tapered profile for pushing through tissue whenadvanced over a wire or dilator.

FIGS. 2 and 3 provide various cross-sectional views of an exampleexpandable sheath 10. The sheath 10 has a tubular wall structureincluding an elastic outer tubular layer 40 and an inner tubular layer42. FIGS. 2 and 3 illustrate the inner tubular layer 42 and elasticouter tubular layer 40 in a non-expanded state. In the non-expandedstate, a portion of the inner tubular layer 42 is folded over uponitself to fit within the central lumen 58 of the outer tubular layer 40.In some embodiments, the inner and outer tubular layers 42, 40 can beadhered to each other at the distal end of the sheath 10 in a sealedconfiguration.

FIG. 4 provides a cross-sectional view of an example inner tubular layer42 in an expanded state. As illustrated in FIG. 4 , the inner tubularlayer 42 can include a thick wall portion 62 integrally connected with athin wall portion 64. The thick wall portion 62 is approximately 0.011+/- 0.003 inches and the thin wall portion 64 is approximately 0.0055+/-0.0020 inches. The inner tubular layer 42 is preferably constructedof a relatively (compared to the outer tubular layer 40) stiff materialsuch as a stiff polymer like high density polyethylene (HDPE) or anequivalent polymer.

The thick wall portion 62, in the illustrated embodiment of FIG. 4 , hasa C-shaped cross-section with a first longitudinally extending end 66and a second longitudinally extending end 68. At the ends 66, 68, thethickness of the thick wall portion 62 starts to narrow to thin wallportion 64 on the cross-section. That transition extends longitudinallyin the direction of the axis of the sheath 10, such that the thick wallportion 62 forms an elongate C-shaped member.

THe thin wall portion 64 extends between the longitudinally extendingends 66, 68 of the thick wall portion 62 to define the tubular shape ofthe inner tubular layer 42. As illustrated in FIGS. 2 and 3 , in thenon-expanded state, the elastic outer tubular layer 40 urges the firstlongitudinally extending end 66 toward and/or under the secondlongitudinally extending end 68 of the inner tubular layer 42. Thiscauses the thin wall portion 64 to fold and be positioned between thefirst and second longitudinally extending ends 66, 68 of the thick wallportion 62.

In an example sheath 10, the central lumen 38 of the inner tubular layer42, in the expanded state, has a diameter larger than the initial,non-expanded, diameter of the central lumen 58 of the elastic outertubular layer 40. For example, the expanded diameter of the centrallumen 38 of the inner tubular layer 42 is about 0.300 +/- 0.005 inches.The initial, non-expanded, diameter of the central lumen 58 of the outertubular layer 40 is about 0.185 inches. In another example, the expandeddiameter of the central lumen 38 of the inner tubular layer is about0.255 +/- 0.005 inches and the initial, non-expanded, diameter of thecentral lumen 58 of the outer tubular layer 40 is about 0.165 inches +/-0.005. The elastic outer tubular layer 40 can expand to accommodate thisincrease in diameter of the inner tubular layer 42.

FIG. 5 provides a cross-sectional view of an example outer tubular layer40. As illustrated, the outer tubular layer 40 has a cylindrical shapewith a circular cross-section along its entire length. The outer tubularlayer 40 defines a central lumen 58 extending axially through itscylindrical cross-section. The diameter of the outer tubular layer 40 inits fully expanded state is sized so as to accommodate the implant andits delivery apparatus 110. In one example sheath, upon expansion, thediameter of the central lumen 58 of the outer tubular layer 40 can be0.322 inches, the outer tubular layer itself having a wall thickness of0.005 +/- 0.003 inches to accommodate delivery of a stent-mounted heartvalve. In one aspect, inner surface of the outer tubular layer 40 and/orouter surface of the inner tubular layer 42 can be treated to have orhave applied thereto a lubricious coating to facilitate unfolding andfolding of the inner tubular layer 42.

The central lumen 58 of the outer tubular layer 40 is referred to ashaving “initial” diameter to designate its passive, non-expanded, oras-formed diameter or cross-sectional dimension when not under theinfluence of outside forces, such as the implant 112 and its deliverysystem passing therethrough. In an example sheath 10, the outer tubularlayer 40 can be constructed from an elastic material and may not retainits shape under even light forces such as gravity. Also, the outertubular layer 40 need not have a cylindrical cross-section and insteadcould have oval, square or any other regular or irregular shape incross-section which generally can be configured to meet the requirementsof the inner tubular layer 42 and/or expected shape of the implant 112.Thus, the term “tube” or “tubular” as used herein is not meant to limitshapes to circular cross-sections. Instead, tube or tubular can refer toany elongate structure with a closed-cross section and lumen extendingaxially therethrough.

The outer tubular layer 40, in one implementation, is constructed of arelatively elastic material having sufficient flexibility to accommodatethe expansion induced by passage of the implant and its delivery systemand expansion of the inner tubular layer 42 while, at the same time,having enough material stiffness to urge the inner tubular layer 42 backinto/towards a non-expanded state having an approximation of the initialdiameter once the implant has passed. An exemplary material includesNEUSOFT. NEUSOFT is a translucent polyether urethane based material withgood elasticity, vibration dampening, abrasion and tear resistance. Thepolyurethanes are chemically resistant to hydrolysis and suitable forovermolding on polyolefins, ABS, PC, Pebax and nylon. The polyuerthaneprovides a good moisture and oxygen barrier as well as UV stability. Oneadvantage of the outer tubular layer 40 is that it provides a fluidbarrier for the pressurized blood. Other materials having similarproperties of elasticity can also be used for the elastic outer tubularlayer 40.

FIGS. 6A-6C illustrate a cross-sectional view of an example sheath 10including one or more longitudinally oriented stiffening elements, suchas rods 60. Advantageously, the longitudinal rods 60 are configured toprovide a bearing surface to facilitate relative movement of thedelivery apparatus 110 and/or prosthetic implant 112 within the innertubular layer 42. This is especially helpful when the inner tubularlayer 42 is unfolding and returning (fully or partially) to itsoriginally folded shape upon passage of the delivery apparatus110/prosthetic implant 112.

A sheath 10 with rods 60 coupled only to the thin wall portion 64 isshown in cross-section in the non-expanded state in FIG. 6A and theexpanded state in FIG. 6B. When coupled to the thin wall portion 64 ofthe inner tubular layer 42, the longitudinal rods 60 reduce frictionbetween the thin wall portion 64 and the adjacent thick wall section 62,making it easier for them to slide against each other. This reduction infriction facilitates unfolding during expansion of the sheath 10,decreasing the required push force to move the prosthetic implant andits delivery system through the sheath 10. The consistency anduniformity of the push force is also increased by the because theprocess of unfolding occurs at specific, incremental points along thethin wall segment. For example, during local expansion of the sheath 10,the inner tubular layer 42 can incrementally expand or have agradual/segmented expansion such that the unfolding of the thin wallportion 64 progresses gradually between ends 66, 68 and rods 60. In oneexample, the incremental expansion progresses from the first end 66 tothe next adjacent rod 60, to the next adjacent rod 60, and so forthbetween the rods 60, to the second end 68, until the inner tubularmember 42 is in the expanded state and the thin wall portion 64 is nolonger folded.

FIG. 6C shows longitudinal rods 60 embedded within and spaced aroundboth the thick wall portion 62 and the thin wall portion 64, with theembedded rods 60 protruding from both the inner and outer surfaces ofthe inner tubular layer 42. Longitudinal rods 60 can be embedded withinjust the thin wall portion 64, as shown in FIGS. 6A and 6B, or thelongitudinal rods 60 can be embedded within and spaced around both thethick wall portion 62 and the thin wall portion 64, as shown in FIG. 6C.The length or width of a longitudinal rod 60 positioned in the thin wallportion 64 of inner tubular layer 42 can be the same size aslongitudinal rods 60 positioned in the thick wall portion 62, or adifferent size.

The longitudinal rods 60 can have a circular cross-section so as topresent a curved bearing surface into central lumen 38 of the innertubular layer 42 and/or central lumen 58 of the outer tubular layer 40.In this manner, the longitudinal rods 60 space the inner tubular layer42 from the inner surface of the outer tubular layer 40 and/or the outersurface of the delivery apparatus 110/implant 112, thus reducingfriction or the tendency to stick and impede relative movement. Althoughdiameters for the longitudinal rods 60 can vary, in one embodiment theyare 0.005+/-0.004 inches in diameter. In some examples, the longitudinalrod 60 extends from the inner and/or outer surface of the inner tubularlayer 42 about 0.004+/-0.003 inches. In other embodiments, thelongitudinal rods 60 can define other shapes in cross-section. It isalso contemplated that the cross-sectional shape of the longitudinal rod60 can change along the sheath 10 in the longitudinal direction.Alternatively, the longitudinal rods 60 can be completely encapsulatedwithin the thin wall portion 64 of the inner tubular layer 42; that is,the outer diameter of the rods 60 can be equal to or less than thethickness of the thin wall portion 64. In this manner, the rods 60provide the described reinforcing structure and facilitate incrementalunfolding/expansion of the inner tubular layer 42, while providingrelatively minimal friction reducing capabilities. The longitudinal rods60 can be composed of the same or different material as the innertubular layer 42. The longitudinal rods 60 can be coupled to the innertubular layer 42 by co-extrusion, and/or embedded or otherwise coupledto the elastic material of the inner tubular layer 42.

When the sheath 10 is in the unexpanded configuration, as in FIG. 6A,the longitudinal rods 60 contact the thick wall portion 62 on both theinner and outer surfaces of the inner tubular layer 42, spacing thethick wall portion 62 from the thin wall portion 64. The decreasedcontact area between the thick and thin wall portions 62, 64 diminishesthe friction between the surfaces during sheath expansion. The decreasedfriction translates to a lower push force, i.e., less force is requiredto move the implant and its delivery system through the sheath 10 andtowards the procedure site. Coupling longitudinal rods 60 to the thinwall portion 64 can also increase the consistency and uniformity of thepush force as the implant and its delivery apparatus 110 travel alongthe length of sheath 10. Without the longitudinal rods 60, the thick andthin wall portions 62, 64 can separate from each other at randomintervals along the thin wall portion 64 during unfolding. When thelongitudinal rods 60 are present, the folding points predictably occurat expected locations. For example, if the rods 60 were formed of amaterial with lower rigidity than the surrounding thin wall portion 64,the folding point could occur at the rod 60. If the rods 60 were formedof a material with higher rigidity than the surrounding thin wallportion 64, the folding point could occur in the thin wall portion 64,at a position between two adjacent rods. The predictable unfoldingpattern translates to a consistent push force. The lowered push forceand increased push force consistency that results from includinglongitudinal rods in the thin wall portion 64 can be especiallybeneficial for sheaths having small outer diameters, for example fromabout 10 French to about 14 French, including about 10 French, about 11French, about 12 French, about 13 French, and about 14 French.

FIGS. 7A-7C provide another example of sheath 10 including a pluralityof longitudinal rods 60 coupled to the inner tubular layer 42.Longitudinal rods 60 can be embedded within just the thin wall portion64, as shown in FIGS. 7A and 7B, or the longitudinal rods 60 can beembedded within and spaced around both the thick wall portion 62 and thethin wall portion 64, as shown in FIG. 7C. The length or width of alongitudinal rod 60 positioned in the thin wall portion 64 of innertubular layer 42 can be the same size as longitudinal rods 60 positionedin the thick wall portion 62, or a different size. The longitudinal rods60 are positioned such that they protrude from the outer surface of theinner tubular layer 42, toward the outer tubular layer 40. In thenon-expanded state shown in FIG. 7A, the longitudinal rods 60 of thethin wall portion 64 contact the thick wall portion 62 on the outersurface of the inner tubular layer 42.

FIGS. 8A-8C provide another example sheath 10 including a plurality oflongitudinal rods 60 coupled to the inner tubular layer 42. Longitudinalrods 60 can be embedded within just the thin wall portion 64, as shownin FIGS. 8A and 8B, or the longitudinal rods 60 can be embedded withinand spaced around both the thick wall portion 62 and the thin wallportion 64, as shown in FIG. 8C. The length or width of a longitudinalrod 60 positioned in the thin wall portion 64 of inner tubular layer 42can be the same size as longitudinal rods 60 positioned in the thickwall portion 62, or a different size. The longitudinal rods 60 arepositioned such that they protrude from the inner surface of the thinwall portion 64 of inner tubular layer 42. In the non-expanded state, asillustrated in FIG. 8A, the longitudinal rods 60 come into contact withthe thick wall portion 62 on the inner surface of inner tubular layer42.

While the embodiments shown in FIGS. 6-8 illustrate three longitudinalrods 60 coupled to the thin wall portion 64, the number of longitudinalrods 60 can vary. Some embodiments can have as few as two or as many as30 longitudinal rods 60 coupled to the thin wall portion 64. A largenumber of longitudinal rods 60-even 100 or more, depending upon theircross-sectional size, can be embedded in and spaced, evenly or unevenly,around the circumference of inner tubular layer 42. As described above,the cross-sectional shape of the longitudinal rods 60 can also vary. Thelongitudinal rods 60 shown in FIGS. 6-8 are circular in cross-section,but in other embodiments the longitudinal rods can be elliptical orsemi-circular, or any other regular or irregular shape in cross-section.In some embodiments, the longitudinal rods 60 coupled to the innertubular layer 42 extend the entire length of inner tubular layer 42.However, it is contemplated that in other embodiments, the longitudinalrods 60 will extend only a portion of the length of the inner tubularlayer 42. In some embodiments, the inner tubular layer 42 can havelongitudinal rods with a variety of radial positions. For example, somelongitudinal rods 60 may protrude from both the inner and outer surfacesof the inner tubular layer 42, while other longitudinal rods 60 mayprotrude from just the inner surface, just the outer surface, or beentirely encapsulated within the inner tubular layer 42. It is furthercontemplated that longitudinal rods 60 can be included in only the thickwall portion 62 of the inner tubular layer 42. The longitudinal rods 60can extend along the entire length of the inner tubular layer 42 oralong a portion of the length of the inner tubular layer 42.

As shown in FIGS. 9-14 , elastic outer tubular layer 40 can also includelongitudinal rods 60. As illustrated in FIG. 9 the elastic outer tubularlayer 40 can include a plurality of longitudinal rods 60. Thelongitudinal rods 60 extend the length of the outer tubular layer 40 andextend into the central lumen 58. The longitudinal rods 60 are coupledto the outer tubular layer 40, such as by being co-extruded and/orembedded into the elastic material of the outer tubular layer 40.Advantageously, the longitudinal rods 60 are configured to provide abearing surface to facilitate relative movement of the inner tubularlayer 42 within the outer tubular layer 40. This is especially helpfulwhen the inner tubular layer 42 is unfolding and returning to itsoriginally folded shape.

The longitudinal rods 60 can be circumferentially spaced about theinside surface of the outer tubular layer 60. Although fifteenlongitudinal rods 60 are shown in the cross-section of FIG. 9 , anynumber, including a single one, of longitudinal rods 60 can be employed.Also, the longitudinal rods 60 need not extend the entire length of theouter tubular layer 60. They can instead be applied selectivelydepending upon the demands of the implant, application and othercircumstances. Longitudinal rods 60 can be selectively left out of anoverall spacing pattern, such as in the embodiment shown in FIG. 9 whereapproximately 90-degrees of the inside surface of the outer tubularlayer 40 is left as an unadorned surface.

FIG. 10 provides an enlarged view of a portion of the outer tubularlayer 40 of FIG. 9 . As shown in FIG. 10 , the longitudinal rods 60 canhave a circular cross-section so as to present a curved bearing surfaceinto the lumen 58. In this manner, the longitudinal rods 60 space theinner tubular layer 42 from the inner surface of the outer tubular layer40, thus reducing friction or the tendency to stick and impede relativemovement. Although diameters for the longitudinal rods 60 can vary, inone embodiment they are 0.005+/-0.004 inches in diameter. In someexamples, the longitudinal rods 60 extend from the inner surface of theouter tubular layer 40 about 0.004 inches. In other embodiments, thelongitudinal rods 60 can define other shapes in cross-section. It isalso contemplated that the cross-sectional shape of the longitudinal rod60 can change along the sheath 10 in the longitudinal direction. Asdescribed above and illustrated in FIG. 10 , the longitudinal rods 60can be fully or partially encapsulated/enclosed within the material ofthe outer tubular layer 40. This prevents the longitudinal rods 60 frommoving circumferentially and provides extra stability to the outertubular layer 40. For example, as illustrated in FIG. 10 , a majority ofthe perimeter of the longitudinal rods 60, i.e., more than 50-percent ofthe perimeter, can be enclosed within the outer tubular layer 40. Asprovided in FIG. 10 , the wall thickness of the outer tubular layer 40increases slightly proximate the longitudinal rod 60 such that the innersurface of the outer tubular layer 40 extends along the circumference ofthe longitudinal rod 60 to the portion where the rod 60 protrudes intothe central lumen 58 of the outer tubular layer 40.

FIG. 11 illustrates a sheath 10 including seven longitudinal rods 60equally spaced from each other about the inner surface of the outertubular layer 40 with the exception that a rod is missing from a portionadjacent the fold in the inner tubular layer 42. This gap inlongitudinal rods 60 facilitates expansion and return of the innertubular layer 42 to a non-expanded state. The gap in longitudinal rods60 also functions as an anchor (a region of heightened friction) toprevent the outer tubular layer 40 from rotating against the innertubular layer 42 during expansion and return of the sheath 10.

FIG. 12 illustrates an example sheath 10 wherein longitudinal rods 60are embedded in and spaced around the circumference of the outer tubularlayer 40 with the exception that a rod 60 is missing from a portionopposite the fold in the inner tubular layer 42. This gap in thelongitudinal rods 60 facilitates distraction and ensures that theportion of the outer tubular layer 40 without longitudinal rods 60 (thegap portion) functions as an anchor to prevent the outer tubular layer40 from rotating against the inner tubular layer 42 during expansion andreturn of the sheath 10. As illustrated in FIG. 12 , the longitudinalrods 60 protrude from the outer surface of the outer tubular layer 40 tolower friction between the sheath 10 and a body lumen or additionalouter delivery sheath. The longitudinal rods 60 also protrude from theinner surface of the outer tubular layer 40 and into the central lumen58 to lower friction between the outer tubular layer 40 and the innertubular layer 42 during expansion and return of the inner tubular layer42 to a non-expanded state.

FIG. 13 illustrates a similar rod arrangement to FIG. 11 , but witheight longitudinal rods 60 embedded in and spaced around thecircumference of outer tubular layer 40. Similar to the arrangement ofFIG. 11 , the rods 60 are offset from the location of the fold in theinner tubular layer 42 to facilitate expansion and return of the innertubular layer 42 to a non-expanded state. Furthermore, the rods 60 ofFIG. 13 protrude from the outer surface of the outer tubular layer 40 tolower friction between the sheath 10 and a body lumen or an additionalouter delivery sheath. The longitudinal rods 60 also protrude from theinner surface of the outer tubular layer 40 and into the central lumen58 to lower friction between the outer tubular layer 40 and the innertubular layer 42 during expansion and return of the sheath 10 to anon-expanded state.

FIG. 14 illustrates an example sheath 10 wherein longitudinal rods 60are embedded in and spaced around the circumference of the outer tubularlayer 40. As provided in FIG. 14 , some of the longitudinal rods 60protrude into the central lumen 58 of the outer tubular layer 42, andsome of the longitudinal rods 60 protrude from the outer surface of theouter tubular layer 42. The inward and outward projection of thelongitudinal rods 60 alternates around the circumference of the outertubular layer 42. This can lower friction from advancement of the sheath10 wherein, for example, the outer surface of the outer tubular layer 40touches a body lumen or additional outer delivery sheath. Thelongitudinal rods 60 protruding from the inner surface of the outertubular layer 40 and into the central lumen 58 lower friction betweenthe outer tubular layer 40 and the inner tubular layer 42 duringexpansion and return of the sheath 10 to a non-expanded state.

FIG. 15 provides another example sheath 10 wherein the longitudinal rods60 are embedded in and spaced around the circumference of the outertubular layer 40. The longitudinal rods 60 protrude from the innersurface of the outer tubular layer 40 and into the central lumen 58 tolower friction between the outer tubular layer 40 and the inner tubularlayer 42 during expansion and return of the inner tubular layer 42 to anon-expanded state. As illustrated in FIG. 15 , individual longitudinalrods 60 protrude into the central lumen 58 to various depths around thecircumference of the outer tubular layer 40. Also, at least one of thelongitudinal rods 60 protrudes from the outer surface of the outertubular layer 40. It is also contemplated, and several longitudinal rods60 can protrude from the outer surface of the outer tubular layer 40,and that the individual longitudinal rods 60 can protrude from the outersurface at varying distances.

In any of the embodiments, multiple longitudinal rods 60 may be spacedevenly or unevenly around the circumference of the inner tubular layer42. Likewise, multiple longitudinal rods 60 can be spaced evenly orunevenly around the circumference of the outer tubular layer 40.

The outer tubular layer 40 in the configurations of FIGS. 9-15 can havea highly elastic and thin structure to fit over the inner tubular layer42. The outer tubular layer 40 is not adhered to the inner tubular layer42 allowing for free movement between the two layers. The outer tubularlayer 40 is also seamless to guard against blood leakage. The outertubular layer 40 promotes even stretching of sheath 10 in all radialdirections-reducing the risk that the sheath 10 will tear duringexpansion. As described above, the elastic outer tubular layer 40 alsourges the inner tubular layer 42 back into the non-expanded, reducedprofile configuration. The outer tubular layer 40 can include a largenumber of longitudinal rods 60-even 100 or more depending upon theircross-sectional size. The longitudinal rods 60 can includemicrostructure patterns on their surfaces. For example, a microstructurepattern protruding from an outer surface of the longitudinal rod 60 canfurther reduce the contact surface between the longitudinal rod 60 andthe inner tubular layer 42, further reducing friction between the two.

Expandable sheaths of the present disclosure can be used with variousmethods of introducing a prosthetic device into a patient’s vasculature.Generally, during use, the expandable sheath 10 is passed through theskin of patient (usually over a guidewire) such that the distal endregion of the expandable sheath 10 is inserted into a vessel, such as afemoral artery, and then advanced to a wider vessel, such as theabdominal aorta. The delivery apparatus 110 and its prosthetic device isthen inserted through the expandable sheath 10 and advanced through thepatient’s vasculature until the prosthetic device is delivered to theimplantation site and implanted within the patient. During the advanceof the prosthetic device through the expandable sheath 10, the deviceand its delivery system exerts a radially outwardly directed force on aportion of the inner tubular layer 42, that portion of the inner tubularlayer 42 exerts a corresponding radially outwardly directed force on aportion of the outer tubular layer 40, causing both the inner tubularlayer 42 and the outer tubular layer 40 to expand locally to accommodatethe profile of the device. The expansion of the inner tubular layer 42causes the first and second longitudinally extending ends 66, 68 of thethick wall portion 62 to radially expand/separate. As a result, the thinwall portion 64 unfolds from its contracted state to define the expandeddiameter of the inner tubular layer 42. As described above, duringexpansion, rods 60 provided on the inner tubular layer 42 and/or outertubular layer 40 facilitate relative movement between the inner andouter layers 42, 40 and the passing device. The rods 60 provided on thethin wall portion 64 also facilitate an incremental or segmentedexpansion of the sheath 10. As outlined above, the inner tubular layer42 will unfold progressively between the ends 66, 68 and the rods 60(e.g., first incremental expansion provided between the first end 66 andthe first adjacent rod 60, the second increment of expansion providedbetween the first rod 60 and the second rod 60, the third increment ofexpansion provided between the second rod 60 and the third rod 60, andthe fourth increment of expansion provided between the third rod 60 andthe end 68). It is contemplated that the incremental expansion may occurin any order between end 66 and end 68.

As the prosthetic device and its delivery system passes through theexpandable sheath 10, the expandable sheath 10 recovers. That is, itreturns to its original, non-expanded configuration. The outer tubularlayer can provide an inwardly directed radial force to exert acompressive force urging the inner tubular layer 42 towards thenon-expanded state. The outer tubular layer 40 can urge the first andsecond longitudinally extending ends 66, 68 toward and/or under, eachother, after the passage of the prosthetic implant 112, such that theends 66, and 68 of the inner tubular member 42 overlap when in thenon-expanded state, with the thin wall portion 64 extendingtherebetween.

As described above, the expandable sheath 10 can be used to deliver,remove, repair, and/or replace a prosthetic device. In one example, theexpandable sheath 10 described above can be used to deliver a prostheticheart valve to a patient. For example, a heart valve (in a crimped orcompressed state) can be placed on the distal end portion of anelongated delivery catheter and inserted into the sheath. Next, thedelivery catheter and heart valve can be advanced through the patient’svasculature to the treatment site, where the valve is implanted.

Beyond transcatheter heart valves, the expandable sheath 10 can beuseful for other types of minimally invasive surgery, such as anysurgery requiring introduction of an apparatus into a subject’s vessel.For example, the expandable sheath 10 can be used to introduce othertypes of delivery apparatus for placing various types of intraluminaldevices (e.g., stents, stented grafts, balloon catheters for angioplastyprocedures, etc.) into many types of vascular and non-vascular bodylumens (e.g., veins, arteries, esophagus, ducts of the biliary tree,intestine, urethra, fallopian tube, other endocrine or exocrine ducts,etc.).

Although the foregoing embodiments of the present disclosure have beendescribed in some detail by way of illustration and example for purposesof clarity and understanding, it will be apparent to those skilled inthe art that certain changes and modifications may be practiced withinthe spirit and scope of the present disclosure. It is intended that thescope of the present invention herein disclosed should not be limited bythe particular disclosed embodiments described above, but should bedetermined only by a fair reading of the claims that follow.

What is claimed is:
 1. An expandable sheath comprising: an elastic outertubular layer comprising a longitudinal rod, the longitudinal rodcomprising a surface that protrudes from the outer tubular layer; and aninner tubular layer extending through the outer tubular layer andradially movable between an expanded state and a non-expanded state, theinner tubular layer having a thick wall portion, the thick wall portionintegrally connected to a thin wall portion that is thinner in a radialdirection than the thick wall portion; wherein the thin wall portionextends between first and second longitudinally extending ends of thethick wall portion, and in the expanded state the first and secondlongitudinally extending ends of the thick wall portion expand apartwith the thin wall portion extending therebetween; wherein in thenon-expanded state the first longitudinally extending end is positionedunder the second longitudinally extending end and the thin wall portionis sandwiched between two segments of the thick wall portion; whereinthe thin wall portion comprises a first reinforcing member extendingalong a length of the thin wall portion and the thick wall portioncomprises a second reinforcing member extending along a length of thethick wall portion; and wherein a surface of each of the first andsecond reinforcing members protrudes from an inner tubular layersurface.
 2. An expandable sheath comprising: an elastic outer tubularlayer comprising a longitudinal rod, the longitudinal rod comprising asurface that protrudes from the outer tubular layer; and an innertubular layer extending through the outer tubular layer and radiallymovable between an expanded state and a non-expanded state, the innertubular layer having a thick wall portion, the thick wall portionintegrally connected to a thin wall portion that is thinner in a radialdirection than the thick wall portion; wherein the thin wall portionextends between first and second longitudinally extending ends of thethick wall portion, and in the expanded state the first and secondlongitudinally extending ends of the thick wall portion expand apartwith the thin wall portion extending therebetween; wherein in thenon-expanded state the first longitudinally extending end is positionedunder the second longitudinally extending end and the thin wall portionis sandwiched between two segments of the thick wall portion; andwherein the inner tubular layer comprises a reinforcing member extendingalong a length of the inner tubular layer with a surface of thereinforcing member protruding from a surface of the inner tubular layer.3. The expandable sheath of claim 2, wherein the longitudinal rodextends along an entire length of the outer tubular layer.
 4. Theexpandable sheath of claim 2, wherein the longitudinal rod is embeddedin the outer tubular layer.
 5. The expandable sheath of claim 2, whereinthe longitudinal rod has a rectilinear shape in cross-section.
 6. Theexpandable sheath of claim 2, wherein the longitudinal rod has acurvilinear shape in cross-section.
 7. The expandable sheath of claim 2,wherein the surface of the longitudinal rod protruding from the outertubular layer protrudes into a central lumen defined by the outertubular layer such that the longitudinal rod provides a bearing surfaceto facilitate relative movement of the inner tubular layer within theouter tubular layer when moving between the expanded and non-expandedstate.
 8. The expandable sheath of claim 7, wherein the longitudinal rodis a first longitudinal rod, and wherein the outer tubular layer furthercomprises a second longitudinal rod spaced circumferentially from thefirst longitudinal rod, a surface of the second longitudinal rodprotruding from an outer surface of the outer tubular layer such thatthe second longitudinal rod provides a bearing surface to easelongitudinal movement of the outer tubular layer relative to a bodylumen or an outer delivery sheath.
 9. The expandable sheath of claim 8,wherein the outer tubular layer comprises a plurality of additionallongitudinal rods positioned around a circumference of the outer tubularlayer.
 10. The expandable sheath of claim 2, wherein an outer tubularlayer distal portion and an inner tubular layer distal portion areadhered to each other in a sealed configuration.
 11. The expandablesheath of claim 2, wherein the outer tubular layer is radially movablewith the inner tubular layer between the expanded state and thenon-expanded state, and wherein the outer tubular layer urges the innertubular layer towards the non-expanded state.
 12. The expandable sheathof claim 2, wherein the reinforcing member of the inner tubular layer iscoupled to the thin wall portion of the inner tubular layer.
 13. Theexpandable sheath of claim 12, wherein the reinforcing member extendsalong an entire length of the inner tubular layer.
 14. The expandablesheath of claim 12, wherein the reinforcing member is embedded in thethin wall portion.
 15. An expandable sheath comprising: an inner tubularlayer radially movable between an expanded state and a non-expandedstate, the inner tubular layer having a thick wall portion, the thickwall portion integrally connected to a thin wall portion that is thinnerin a radial direction than the thick wall portion; wherein the thin wallportion extends between first and second longitudinally extending endsof the thick wall portion, and in the expanded state the first andsecond longitudinally extending ends of the thick wall portion expandapart with the thin wall portion extending therebetween; wherein in thenon-expanded state the first longitudinally extending end is positionedunder the second longitudinally extending end such that the thin wallportion is sandwiched between two segments of the thick wall portion;wherein the thin wall portion comprises a first reinforcing memberextending along a length of the thin wall portion and the thick wallportion comprises a second reinforcing member extending along a lengthof the thick wall portion; and wherein a surface of each of the firstand second reinforcing members protrudes from an inner tubular layersurface.
 16. The expandable sheath of claim 15, wherein the first andsecond reinforcing members of the thin wall portion extend along theentire length of the inner tubular layer.
 17. The expandable sheath ofclaim 15, wherein the first and second reinforcing members of the thinwall portion are embedded in the inner tubular layer.
 18. The expandablesheath of claim 15, wherein the thin wall portion comprises a pluralityof first reinforcing members positioned circumferentially around thethin wall portion, and wherein the thick wall portion comprises aplurality of second reinforcing members positioned circumferentiallyaround the thick wall portion.
 19. The expandable sheath of claim 15,wherein the first or second reinforcing member has a rectilinear shapein cross-section.
 20. The expandable sheath of claim 15, wherein thefirst or second reinforcing member has a curvilinear shape incross-section.